DLL4 and T-cell acute lymphoblastic leukemia: Studies have shown that, overexpression of the Notch signaling ligand DLL4 (delta-like 4) in endothelial cells can promote T-ALL (T-cell acute lymphoblastic leukemia) cells to exit dormancy by binding to the Notch3 receptor on T-ALL cells, and this overexpression of DLL4 can be induced by VEGF (144).